Improve CSS for main page

- Breadcrumb now appears above sidenav tree
- Better margin / etc

InvenTree/templates/base.html

@@ -52,19 +52,26 @@ InvenTree
 
 <div class='main body wrapper'>
 
+<div class='inventree-body'>
+
+<div class='containter-fluid inventree-pre-content'>    
+    {% block pre_content %}
+    {% endblock %}
+</div>
+
 <div class='sidenav' id='sidenav'>
 {% block sidenav %}
 {% endblock %}
 </div>
-
+    
 <div class="container container-fluid inventree-content" id='inventree-content'>
-{% block pre_content %}
-{% endblock %}
 {% block content %}
 <!-- Each view fills in here.. -->
 {% endblock %}
+
 {% block post_content %}
 {% endblock %}
+
 </div>
 
 {% include 'modals.html' %}
@@ -72,6 +79,8 @@ InvenTree
 {% include 'notification.html' %}
 </div>
 
+</div>
+
 <!-- Scripts -->
 <script type="text/javascript" src="{% static 'script/jquery_3.3.1_jquery.min.js' %}"></script>
 <script type='text/javascript' src="{% static 'script/jquery.form.min.js' %}"></script>